This invention relates to technologies for managing wet printed media output in printing mechanisms.
In certain types of printing mechanisms such as inkjet printers, a printed media sheet may remain wet for a period after images have been imprinted on it. It is generally desired that such a wet printout be dried before it is ejected onto an output tray to avoid possible smearing of the images on the previously ejected media sheets. Holding members such as ramps and wing structures are commonly used to hold the wet printed media sheet for a desired distance before the printed media sheet moves onto the output tray.
FIG. 1 illustrates such a pair of wings 101 in an inkjet printer. The wings 101 are mounted to the printer frame 103 at two sides of the printer along the media width and positioned in front of the output roller 105 in the output direction as indicated by arrow 111, in which the output roller 105 propels the printed media sheet 107 into an output area 109. The wings 101 project upward at an angle and accordingly lift up two sides of the printed media sheet 107. As a result, the front portion of the media sheet 107 that has passed the output roller 105 is curled upwards. Such a change of shape allows the media sheet 107 to sustain itself for some desired distance before it falls onto the output tray (not shown) on its own weight. Furthermore, the shape change of the media sheet 107 also creates a stress on the media sheet 107.
However, the stress causes a retarding force on the media sheet opposite to its forward motion along the output direction. Such a retarding force may affect the linefeed accuracy of the media sheet. Especially, when the media sheet has just met the wings, the sudden change in the stress and consequently the sudden change in the retarding force may cause a jerking effect on the media advancement, which may affect the linefeed of the media sheet. Generally, the larger amount of the stress on the media sheet, the larger amount of the retarding force is caused, and the more significantly the linefeed accuracy can be affected.
The stress is affected by both the shape change and the stiffness of the media sheet 107; the stiffness of the media sheet 107 can be affected by its material, thickness, width and so on. Conventionally, the wings 101 are rigidly mounted to the printer frame 103, and therefore the amount of the shape change remains almost identical regardless of the variation in the stiffness of the media sheet. Consequently, the stress on the media sheet 107 varies corresponding to the variation in the stiffness of the media sheet 107. In particular, the stiffer the media sheet, the larger amount of stress is exerted on the media sheet
In the conventional designs, the wings are oriented based upon media having a relatively small amount of stiffness so that most types of media can be held for at least a desired distance during the ejection. However, when a stiffer media sheet is used, a larger amount of stress more than necessary Is caused. Such a larger amount of stress may not be desirable in that it may affect the linefeed accuracy of the media sheet significantly.
Modifications have been made to optimize such a stress on the media sheet of various stiffness. For example, retractable holding members disclosed in U.S. Pat. No. 6,148,727, entitled xe2x80x9cWet Printed Media Output Mechanism Systemxe2x80x9d and assigned to the current assignee, Hewlett-Packard Company, CA, can be used to at least partially solve the problem. However, such a mechanism requires relatively complicated synchronization between the movements of the holding members and other parts of the output system.
Therefore, them is a need for a convenient way of optimizing the stress on the printed media sheet exerted by the holding members of a wet printed media output system in a printing mechanism.
According to an aspect of the present invention, there is provided a wet printed media output system in a printing mechanism including a frame. The system includes an ejection mechanism mounted to the frame for ejecting a wet printed medium along a media path in an output direction towards an output area and a holding member mounted to the frame adjacent to the ejection mechanism. A portion of the holding member projects out of the media path at an angle to a plane defined by the output direction and a trailing edge of the medium for deviating at least a portion of the printed medium from the output direction. Furthermore, the angle is adjustable in correspondence with a character of the printed medium.
According to another aspect of the present invention, in a method for ejecting a wet printed medium in a printing mechanism having a frame, an ejection mechanism mounted to the frame for ejecting the medium along a media path in an output direction towards an output area is provided. Furthermore, a holding member is mounted to the frame adjacent to the ejection mechanism, and a portion of the holding member projects out of the media path at an angle to a plane defined by the output direction and a trailing edge of the medium for deviating at least a portion of the printed medium from the output direction. During the ejection process, the angle is adjusted in correspondence with a character of the printed medium for optimizing a stress on the medium exerted by the holding member.